Memory Width and Byte Alignment | Texas Instruments TMS320C642x DSP

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Peripheral Architecture

2.5Memory Width and Byte Alignment

The DDR2 memory controller supports memory widths of 16 bits and 32 bits. Table 5 summarizes the addressable memory ranges on the DDR2 memory controller. See the device-specific data manual for the memory widths that are supported. Both big-endian and little-endian formats are supported.

Figure 11 shows the byte lanes used on the DDR2 memory controller. The external memory is always right-aligned on the data bus.

Table 5. Addressable Memory Ranges

Memory Width	Maximum addressable bytes per CS space	Description
×16	128 Mbytes	Halfword address
×32	256 Mbytes	Word address

Figure 11. Byte Alignment (Little-Endian Mode)

	DDR2 memory controller data bus
DDR_D[31:24]	DDR_D[23:16]	DDR_D[15:8]	DDR_D[7:0]

32-bit memory device

16-bit memory device

20	DDR2 Memory Controller	SPRUEM4A–November 2007
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Texas Instruments TMS320C642x DSP manual Memory Width and Byte Alignment, Addressable Memory Ranges

Contents

Users Guide Submit Documentation Feedback Contents List of Figures List of Tables Read This First Features Purpose of the Peripheral Industry Standards Compliance Statement Functional Block DiagramSupported Use Case Statement Clock Control Clock Source Clock Configuration PLLC2 ConfigurationMemory Map 3 DDR2 Memory Controller Internal Clock Domains Signal Descriptions DDR2 Memory Controller Signal DescriptionsClock enable Active high Pin Type Description DDR2 Sdram Commands Truth Table for DDR2 Sdram CommandsCommand Function Protocol Descriptions Refresh Mode Refresh Command Dcab Command Deactivation Dcab and Deac Deac Command Actv Command Activation Actv Read Command DDR2 Read Command Write WRT Command DDR2 WRT Command Mode Register Set MRS and Emrs DDR2 MRS and Emrs Command Memory Width and Byte Alignment Addressable Memory Ranges Endianness Support Bit External Memory Bit Field Bit Value Bit Description Bank Configuration Register Fields for Address MappingAddress Mapping Logical Address-to-DDR2 Sdram Address Map for 32-Bit Sdram Logical Address-to-DDR2 Sdram Address Map for 16-bit Sdram Logical Address-to-DDR2 Sdram Address Map DDR2 Sdram Column, Row, and Bank Access DDR2 Memory Controller Interface DDR2 Memory Controller Fifo Description Command Ordering and Scheduling, Advanced Concept Command Starvation Possible Race Condition Self-Refresh Mode Refresh SchedulingRefresh Urgency Levels Urgency Level Description Reset Signal Reset Source Reset ConsiderationsReset Sources VTP IO Buffer Calibration Auto-Initialization Sequence DDR2 Sdram Configuration by MRS Command DDR2 Sdram Configuration by EMRS1 CommandInitializing Configuration Registers DDR2 Memory Controller Peripheral Architecture DMA Event Support Power ManagementInterrupt Support Emulation Considerations Connecting the DDR2 Memory Controller to DDR2 Memory Supported Use Cases Connecting DDR2 Memory Controller for 32-Bit Connection Configuring Sdram Bank Configuration Register Sdbcr Sdram Bank Configuration Register Sdbcr ConfigurationConfiguring Sdram Refresh Control Register Sdrcr DDR2 Memory Refresh Specification Configuring Sdram Timing Registers Sdtimr and SDTIMR2 Sdram Timing Register Sdtimr ConfigurationSdram Timing Register 2 SDTIMR2 Configuration DDR2 Data Register Field Manual Data Manual Formula Register Field Name Description Configuring DDR PHY Control Register DdrphycrDDR PHY Control Register Ddrphycr Configuration Mode D63-32 D31-0Acronym Register Description DDR VTP Register Bit Field Sdram Status Register SdrstatSdram Status Register Sdrstat Field Descriptions Bit Field Value Description Sdram Bank Configuration Register SdbcrSdram Bank Configuration Register Sdbcr Field Descriptions Reserved Reserved. Always write a 0 to this bit Sdram Refresh Control Register Sdrcr Sdram Refresh Control Register Sdrcr Field Descriptions Sdram Timing Register Sdtimr Sdram Timing Register Sdtimr Field Descriptions Sdram Timing Register 2 SDTIMR2 Sdram Timing Register 2 SDTIMR2 Field Descriptions Peripheral Bus Burst Priority Register Pbbpr Peripheral Bus Burst Priority Register Pbbpr Interrupt Raw Register IRR Interrupt Raw Register IRR Field Descriptions Interrupt Masked Register IMR Interrupt Masked Register IMR Field Descriptions Interrupt Mask Set Register Imsr Interrupt Mask Set Register Imsr Field Descriptions Interrupt Mask Clear Register Imcr Interrupt Mask Clear Register Imcr Field Descriptions DDR PHY Control Register Ddrphycr DDR PHY Control Register Ddrphycr Field Descriptions VTP IO Control Register Vtpiocr VTP IO Control Register Vtpiocr Field Descriptions DDR VTP Enable Register Ddrvtper DDR VTP Enable Register Ddrvtper Field DescriptionsDDR VTP Register Ddrvtpr DDR VTP Register Ddrvtpr Field Descriptions Table A-1. Document Revision History Additions/Modifications/Deletions Important Notice